The present invention relates to the production of industrial coatings for metal products. More specifically it relates to the class of industrial coatings known as high solids, oil-free polyester coatings which also have low volatile organic compounds (VOC). It relates to such above coatings which are applied to steel or other metal substrates by the process of hot tank dipping, flow coating, air or electrostatic spraying, and cured by heating to a temperature of 300.degree.-350.degree. F. for a period of time.
High solids coatings of several types are known in the art. The following are known to the applicant and disclosed in U.S. Pat. Nos. 2,284,241--Werntz, 3,436,367--McInerney, 3,485,781--Wallman et al, 4,195,102--Turpin, 4,206,264--Kurr, 4,243,705--Yapp et al, 4,268,547--Backhouse, 4,272,291--Shtern, 4,322,508--Peng et al, and 4,326,888--Frew.
Examination of the prior art reveals compositions for a coating suitable for hot tank dipping. Other compositions appear to be suited for electrostatic spraying or conventional spraying. No compositions have been found which are suitable for either hot tank dipping or spraying, nor any which are stable in a hot dip tank for long periods of time, without congealing, and without substantial solvent loss. Several compositions with desirable features are unable to meet current Environmental Protection Agency guidelines and OSHA requirements. The compositions found in the prior art are unsatisfactory for application to substrates having sharp corners, projections, bolt holes and similar irregularities in shape because of their tendency to run, drip and tear.
The present invention is suitable for use on all surface configuration is including those having rounded or curvilinear shapes, and substrates affixed to any orientation, yielding a coating having a uniform thickness between 1.0 and 1.5 mils on the substrate, and is suitable for prolonged use in a hot dip tank without degradation of the materials.